From: Andi Kleen <andi@firstfloor.org>
To: Stephane Eranian <eranian@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Andi Kleen <andi@firstfloor.org>, "mingo@elte.hu" <mingo@elte.hu>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] perf, x86: Add workaround for MEM_*_RETIRED errata BV98
Date: Wed, 1 May 2013 21:13:42 +0200 [thread overview]
Message-ID: <20130501191342.GH17814@two.firstfloor.org> (raw)
In-Reply-To: <CABPqkBT-VdWQ0c5AASDfQLssBRSfbtoH0-L1eHMXONqe5d_YRw@mail.gmail.com>
> Unfortunately, Andi's patch fails to correct the problem though
> it is the right approach. As he said, the problem is unfortunately
perf stat -a / record -a / top will work.
The case it doesn't fix is per thread when the other sibling
is not running a counter.
Essentially with the patch you may still get under-counting
on these specific events if they run per thread (or are really
unlucky in multiplexing), but never over-counting on anything.
In the past Ingo's guidance was to focus on the most common
use cases, which I think this patch does.
It would be possible to fix the per thread mode too, but it would
need quite a bit of new infrastructure and I have doubts that's
worth it.
-Andi
next prev parent reply other threads:[~2013-05-01 19:13 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-29 18:45 Andi Kleen
2013-05-01 9:07 ` Peter Zijlstra
2013-05-01 9:56 ` Andi Kleen
2013-05-01 10:10 ` Ingo Molnar
2013-05-01 11:12 ` Peter Zijlstra
2013-05-01 18:13 ` Stephane Eranian
2013-05-01 19:13 ` Andi Kleen [this message]
2013-05-01 19:21 ` Stephane Eranian
2013-05-02 7:32 ` Peter Zijlstra
2013-05-06 17:41 ` Stephane Eranian
2013-05-06 19:00 ` Peter Zijlstra
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